Application of solid lubricant coatings to surfaces



United States Patent APPLICATION OF SOLID LUBRICANT COATINGS TO SURFACES Jere E. Brophy and Robert W. Ingraham, Endicott, N.Y., assignors to International Business Machines Corporze tion, New York, N.Y., a corporation of New York Application September 19, 1956, Serial No. 610,848

3 Claims. (Cl. 204-37) This invention relates to a method of providing adherent coatings of solid lubricating materials to surfaces of metal, and non-metals, and in particular to metallic members comprised primarily of fine hardened wires as well as other delicately configured hardened metallic parts.

The method of applying solid lubricating coatings comprised of disulphides, selenides and tellurides of such elements as molybdenum and tungsten is set forth in the patent to C. M. Laffon, In, No. 2,420,886. This method is well suited in its application to unhardened metals but not to hardened metals and alloys, for example, alloys of steel, copper and aluminum, because the intense heat called for in this process would not only undo and thus reform the structure of the alloy but would also cause distortion in the shape of the delicate parts.

It is therefore an object of the invention to provide an improved process for producing adherent coatings of solid lubricant on hardened alloys of steel, copper and aluminum.

Another object is to provide an improved process for producing adherent coatings of solid lubricant on nonmetals, for example, plastics, ferrites, ceramics, glass and the like.

A further object is to provide an improved process for treating the surfaces of fine wires and delicate member, made of hardened alloys, to produce thereon adherent coatings of solid lubricating compounds such as molybdenum disulphide, tungsten disulphide, molybdenum selenide, molybdenum telluride and tungsten telluride.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Figure l is a sectional view of an electroplating arrangement, and

Figure 2 is a sectional View of a heat-treating apparatus for heat treating parts under pressure.

In Fig. 1 there is shown an electroplating arrangement suitable for electroplating, for example, molybdenum metal on delicate wire members. The arrangement comprises a tank 1 containing an electrolyte bath 2 which may, for example, consist of 109.2 grams of ammonium formate, 25.2 grams of molybdenum oxide and 2000 milliliters of distilled water. A platinum anode 3 is placed near the wire members 4.

Current is supplied from a DC. source 5 which has its positive terminal connected to the anode 3 and its negative terminal connected to a cathode bar 6 from which are suspended conducting hangers 7 for supporting the members 4 in the electrolyte bath. Current supplied to the members 4 is approximately 1 ampere per square inch at 25 C. The surface deposit is usually from .00005" to .0001" and is obtained in a very short period of time.

After the electroplating treatment, the plated members are washed in water and dried after which they are placed in the heat-treating apparatus shown in Fig. 2.

This heat-treating apparatus comprises essentially an oven of the type well known in the art which oven is constituted of an insulating enclosure 10 and a floor 1 1. The latter is provided with an inlet 12 whereby a converting gas is introduced into the oven. An outlet 13 including a valve 14 is also provided. The outlet is open when the gas is first admitted so that atmosphere or gases from a previous heat treatment are removed after which the outlet valve 14 is closed. The gas is then pumped into the oven through the inlet until the required pressure is indicated on a pressure gauge -15 adapted to read the internal pressure in the oven. It is understood that suitable access means, not shown, is provided through which the members are passed into and removed from the interior of the oven. The members 4 are arranged on a suitable support 16 so that the desired surfaces are fully exposed to the oven gas under pressure. Suitable means, not shown, are provided to heat the oven gas to the desired degree of temperature. A temperature gauge 17 is provided to indicate the degree of oven temperature.

In accordance with one aspect of the invention, the heat treatment for converting the molybdenum coating on thin hardened steel wires, for example, involved a gas pressure of 400 lbs. p.s.i., a temperature of C. for a period of roughly 110 hours.

For other delicate hardened steel parts, the temperature was kept at 60 C. for approximately 300 hours at a gas pressure of 400 lbs. p.s.i. Yet other heavier parts were maintained at a temperature of C. for a period of 2 hours at a gas pressure of 400 lbs. p.s.i. The converting gas involved in the above treatments was hydrogen sulphide.

For the purpose of the invention, hydrogen selenide and hydrogen telluride gases may be employed when the coatings consist of molybdenum selenide, tungsten selenide, molybdenum telluride and tungsten telluride.

The invention may be applied with equal facility to the preparation of coatings on material other than steel, for example hardened beryllium compounds, magnetic alloys in which a desired permeability is to be maintained after treatment, aluminum alloys, alloys of copper, alloys of zinc and alloys of silver. The temperature ranges of each of the alloys mentioned above should be below their respective melting points and since molybdenum disulphide melts at 1185 C., the temperature range should be below this point for those alloys whose melting points are above 1185 C., the time and gas pressure in each instance depending upon the thickness in the coating desired.

To prevent changing the crystalline structure in the hardened surfaces of parts, the latter should not be subjected during the coating process to temperatures at which such changes would occur, such temperatures being above the critical points which are of course different for different metals and alloys of metals, the critical point being that temperature at which no change in structure, characteristics and form takes place.

The process is especially adaptable to such materials as plastics, ceramics, ferrites, glass, barium titanate and the like. In this group of non-metals, especially the ferrites and the titanates, the latter would lose their electrical characteristics if they were heated above their respective Curie temperatures. These materials must, of course, be subjected to a preliminary coating process whereby a conductive coating is formed on the surfaces prior to subjecting them to the process constituting the invention. This preliminary coating process may be effected for example by dipping the material in graphite, or by the application of a silver flashing.

a 2,902,417 p i While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it Will be understood that various omissions and substitutions and changes in the-form and details of the device illustrated and in its operation may be made by those skilled in the art, Without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

l. The method of applying to a surface of a member composed of an alloy selected from the group consisting of steel, copper-base alloys and aluminum-base alloys, an adherent coating of a solid lubricant of a metallic compound selected from the group consisting of sulphides, selenides and tellurides of tungsten and molybdenum, comprising electroplating the surface of the member to deposit thereon an adherent electroplate of the metal component of the compound and then subjecting the electroplated surface to a converting gas consisting of at least one of the group consisting of sulphide, selenide and telluride gases at a pressure ranging from in excess of atmospheric pressure to about 400 p.s.i. and at a temperature range of from approximately 60 C. to about 125 C. for a period of from 30 hours to 110 hours depending upon the thickness desired of the metallic compound coating being formed on the surface of the member.

2. The method of applying to a surface of a member composed of hardened steel, an adherent coating of a solid lubricant of a metallic compound selected from the group consisting of sulphides, selenides and tellurides of tungsten and molybdenum, comprising electroplating the surface of the member to deposit thereon an adherent electroplate of the metal component of the compound and then subjecting the electroplated surface to a converting gas consisting of at least one of the group consisting of sulphide, selenide and telluride gases at a pressure ranging from in excess of atmospheric pressure to 4 about 400 p.s.i. and at a temperature range of from approximately C. to about 125 C. for a period of from 30 hours to hoursdepending upon the thickness desired of the metallic compound coating being formed on the surface of the member.

3. The method of applying to a surface of wire members composed of an alloy selected from the group consisting of steel, copper-based alloys and aluminum-base alloys, an adherent coating of a solid lubricant of a metallic compound selected from the group consisting of sulphides, selenides and tellurides of tungsten and molybdenum, comprising electroplating the surfaces of the members to deposit thereon an adherent electroplate of the metal component of the compound and then subjecting the electroplated surfaces to a converting gas consisting of at least one of the group consisting of sulphide, helenide and telluride gases at a pressure ranging from in excess of atmospheric pressure to about 400 p.s.i. and at a temperature range of from about 60 C. to approximately C. for a period of from 30 hours to 110 hours depending upon the thickness desired of the metallic compound coating being formed on the surfaces 0 the members.

References Cited in the file of this patent UNITED STATES PATENTS 1,908,188 Ruben May 9, 1933 2,245,561 Nelson et a1. June 17, 1941 2,381,911 Kathe Aug. 14, 1945 2,395,743 Kannenberg et al Feb. 26, 1946 2,417,133 Schweikher Mar. 11, 1947 2,420,886 Lafioon May 20, 1947 2,430,581 Passel Nov. 11, 1947 2,512,141 Ma et al. June 20, 1950 2,540,635 Steier Feb. 6, 1951 2,697,645 Mitchell Dec. 21, 1954 2,776,254 Bart Jan. 1, 1957 2,784,123 Rappaport Mar. 5, 1957 

1. THE METHOD OF APPLYILNG TO A SURFACE OF A MEMBER COMPOSED OF AN ALLOY SELECTED FROM THE GROUP CONSISTING OF STEEL, COPPER-BASE ALLOYS AND ALUMINUM-BASE ALLOYS, AN ADHERENT COATING OF A SOLID LUBRICANT OF A METALLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF SULPHIDES, SEL ENIDES AND TELLURIDES OF TUNGSTEN AND MOLYBDENUM, COMPRISING ELECTROPLATING THE SURFACE OF THE MEMBER TO DEPOSIT THEREON AN ADHERENT ELECTROPLATE OF THE METAL COMPONENT OF THE COMPOUND AND THEN SUBJECTING THE ELECTROPLATED SURFACE TO A CONVERTING GAS CONSISTING OF AT LEAST ONE OF THE GROUP CONSISTING OF SULPHIDE, SELENIDE AND TELLURIDE GASES AT A PRESSURE RANGING FROM IN EXCESS OF ATMOSPHERIC PRESSURE TO ABOUT 400 P.S.I. AND AT A TEMPERATURE RANGE OF FROM APPROXIMATELY 60*C. OT ABOUT 125* C. FOR A PERIOD OF FROM 30 HOURS TO 110 HOURS DEPENDING UPON THE THICHNESS DESIRED OF THE METALLIC COMPOUND COATING BEING FORMED ON THE SURFACE OF THE MEMBER. 